Trace and ultratrace nutrient minerals are added to nutritional foods to attain caloric-based concentrations that provide mineral intakes at levels recommended by the Food and Nutrition Board of the National Research Council (Recommended Dietary Allowances, RDA, incorporated herein by reference) or other recognized official sources. Trace minerals in foods occur at concentrations in the microgram-per-gram range and commonly include iron, copper, zinc and manganese. Ultratrace minerals in foods are in the nanogram-per-gram concentration range; chromium, molybdenum and selenium constitute the ultratrace minerals cited in the current Recommended Dietary Allowances. Typically, water-soluble mineral salts that meet standards of composition and purity, such as those described in the Food Chemicals Codex, are added to supplement levels of nutrients endogenous to a typical food matrix of proteins, carbohydrates, lipids and water. These mineral salts must provide the nutrient elements in preferred oxidation states to enable absorption and bio-utilization. For example, iron needs to be present in premixes as ferrous ion, Fe(II), and chromium must be present as chromic ion, Cr(III). Inorganic chromium(III) salts are absorbed very poorly; typically, the absorption is less than one percent (Linder, 1991). Citrate is a very effective chelator of trace elements, such as Cr(III), and may aid in absorption by removing trace elements from less accessible ligands and keeping them in a soluble form (Lonnerdal, 1989). The advantages of sodium selenate (i.e., selenium(VI)), over sodium selenite (i.e., selenium(IV)), in a nutrient premix recently have been described by Borschel, et al.
Although each mineral salt may be added to a nutritional product on an individual basis, such an approach generally is undesirable for large-scale commercial processes. Principal reasons for this include the need for multiple weighings of individual ingredients, the requirement for routinely measuring the concentration of each element in every batch of product, and the potential regular exposure of certain plant personnel to dusts from individual salts. With a premix, which typically is a previously-prepared mixture of mineral compounds and diluent materials, the correct addition of all minerals can be verified by measurements of the concentrations of one or more "marker" minerals added to the food via the premix. Thus, cost benefits and safety are realized through use of a premix of mineral compounds in the plant environment.
The inherent solubility of chromium chloride hexahydrate, which is commercially available as the dark green isomer trans-[CrCl.sub.2 (H.sub.2 O).sub.4 ]Cl.multidot.2H.sub.2 O, makes it a highly preferred compound for use in nutrient premixes that are added to liquid nutritional products. However, the solubility of this material has been observed to diminish measurably over time when chromium chloride hexahydrate is used as an ingredient in mixtures of nutrient minerals. Approaches to provide and sustain soluble chromium forms in premixes are described as principal components of this invention.
Accordingly, it is an object of the present invention to produce a stable nutritional powder, such as a premix used to prepare liquid or solid nutritional products, which is shelf stable and which may be incorporated into a liquid or solid nutritional product without precipitation of chromium. Such a product may become a part of a nutritionally complete or supplemental product that makes soluble chromium available to the user.
In view of the present disclosure or through practice of the present invention itself, other advantages, or the solution to attendant problems, may become apparent to one of ordinary skill in the art.